2) Dungeons don't teach you anything. They don't teach you crowd control (except 3 or 4 pulls during HoR, making it 'so hard').
They don't teach you rotation because boss die faster than mobs in Scholo60. They don't teach you targetting, just AoE, and if you single target, who cares if it's the tank target or not.
They don't teach you positioning or movement, healer is there to save you whatever happens. Even for the healer it''s easy since the tank usually takes no damage at all.
Ex: Last Occulus I did as healer, damage was spread among the Ret, the DK, the Lock and the bear. Second boss no one moved out of the purple rays - healer will take care of that.
Third boss everyone stays in the ice, and don't even hide from the arcane blast. And stay in the ice even after the boss death. Still only one dies (and I'm not a great healer, just an offspec to shorten the waiting time...). And blames me (sure it's my fault I don't play amazingly enough to overcome his badness).
What makes it even worst is that they were standard 2k dps with a 35k PV bear. Nothing expectional, even 'low end' nowadays. You can go 50% above that with badge gear easily.
Still no wipe and 20 min achievement (the last one I got pre-nerf, a pain)
Result: You see people complaining here about how bad some players are. The truth is: they never had a single chance to improve. It might only start with raiding, if they ever raid.